Vacuum packaging machine

ABSTRACT

The invention relates to a vacuum packaging machine for producing an evacuated packaging of a product, which is disposed between an upper film and a lower film, and which can also be reliably used for thicker cover films or hard packaging. 
     This is solved by means of a vacuum packaging machine which contains a forming station and at least one tool lifter ( 10 ) with tools, comprising an upper tool part ( 13 ) and a lower tool part ( 12 ) and a lifting system, which enables a first and a second lifting or closing movement, wherein at least one tool lifting cylinder ( 19 ) for a vertical lift of the lower tool part ( 12 ) as well as a cylinder shaft ( 15 ) passed through the lower tool part ( 12 ) and having a locking cam ( 16 ) is provided, and the cylinder shaft ( 15 ) is passed through an opening ( 17 ) of the lower tool part ( 12 ), the cross-section of said opening corresponding to that of the locking cam ( 16 ).

The invention relates to a vacuum packaging machine for producing a packaging of a product, which is disposed between an upper film and a lower film.

Vacuum packaging machines for producing a packaging of a product which is disposed between an upper film and a lower film are known, for example for an air-tight and durable packaging of fresh products (fish, meat, cheese, bread, etc.). In the case of simple machines, the product to be packaged is placed in a bag in a vacuum chamber and its lid is closed to evacuate the bag. The evacuated and sealed bag with the product must then be removed again from the vacuum chamber. Filling plates can be fitted at the bottom of the chamber for packages of different height. For a more rational mode of operation, DE-C-2752184 reveals a traversable packaging machine with a housing for a vacuum chamber, which can also be closed tight by a lid. A tray for the product to be packaged sits on a frame, which is arranged in such a way as to be lowerable with the product and the tray in the vacuum chamber. The lifting movement takes place by means of a pneumatic cylinder and a lever mechanism, arranged so as to be movable between the latter and the frame. The evacuated bag for the product is welded for example by means of welding bars. According to DE-C-2752183, the bag ends are pulled in automatically when the lid is closed. The welding takes place by means of a double seam and the bag neck is cut off cleanly along the outer weld seam.

According to EP-B-0593748, the evacuation of the chamber ends as soon as a desired underpressure is reached, depending on the properties of the given product. The side flaps of the packaging material lie between welding bars. After the desired vacuum value has been reached, the welding device is activated. After the welding, atmospheric pressure is again established in the vacuum chamber and the sealed product can be removed.

In another packaging machine (WO 96/11844) with a planar product support in a chamber, the height position of this product support is adjustable in such a way that one of the end parts is assigned to a roller conveyor. The product is fed by means of this roller conveyor in the exit region of the chamber. The product support rests on an adjusting and lifting device with arms arranged in pairs, further lever arms and arm wheels. The adjusting and lifting device is actuated by means of a lifting cylinder.

DE-A-102008033611 reveals a packaging machine for producing a resealable package, wherein the packaging comprises an upper film and a lower film. The machine is a deep-drawing machine with a forming tool, a sealing tool and a cutting unit as well as packaging trays and feed units for the tray film and cover film. In a forming station, the tray film or lower film is heated and formed by means of a forming tool into a packaging. A vertical lift system for the deep-drawing is provided in another known machine of this kind Medium stroke is determined by the tool lifts.

The tray film is much thicker than the cover film, although thicker cover films or hard packaging are also increasingly being required, which calls for an applied pressure dependent on the film thickness. With the known machines, this may be too high to permit the vacuum to be maintained.

Furthermore, EP-A-0895933 discloses a packaging machine with a lifting device for a work station. At least one mobile part is brought into a working position by means of a lifting mechanism, an increased force being required to close the tool parts in this position, e.g. for the forming of a packaging. It comprises first lifting elements for generating a first closing movement of the second tool part against the first tool part, second lifting elements for generating a second closing movement following the first closing movement, wherein the second lifting element has an almost constant force characteristic and is constituted such that the force for the second closing movement is generated when a resistance occurs.

Simpler elements comprise piston-cylinder arrangements with a large active area, which however are costly and have a high air requirement. In the case of a lifting device according to EP-B-0569936, following a first stroke, the piston rod, which is constituted as a counter-bearing at the free end, is lifted by a further amount by inserting a wedge into a recess of the piston rod. In this end position, a force is exerted by the piston rod, said force being greater than the force capable of being applied by the piston-cylinder arrangement. When the wedge is inserted, however, friction occurs which causes correspondingly high material wear. Toggle lever systems are also known.

The problem underlying the invention is to create a vacuum packaging machine for producing an evacuated packaging of a product, which is disposed between an upper film and a lower film, which can also be reliably used for thicker cover films or top films or hard packages and requires a comparatively low expenditure whilst having a high degree of reliability.

The problem is solved with the features of claim 1.

Provided on a vacuum packaging machine is at least one tool lifter, which comprises at least one lifting cylinder for a vertical lift with a cylinder shaft and a locking cam, wherein the cylinder shaft is passed through an opening of the lower tool part, the cross-section of said opening corresponding to that of the locking cam.

Preferred embodiments are disclosed in the dependent claims. This enables the application of a sufficiently high applied pressure with a small space requirement and high operational reliability. The arrangement is simple in structure and almost wear-free.

A constant applied pressure is achieved without further expenditure on correction or adjustment.

The invention is explained in detail below with the aid of a drawing in an example of embodiment, to which the invention is not limited. In the drawing,

FIG. 1: shows a vacuum packaging machine in a simplified representation,

FIG. 2: a tool lifter in partial view,

FIG. 3: a view of the lifting system.

FIG. 1 shows a vacuum packaging machine 1 with a working plane 2 on which the product to be packaged can be placed and conveyed, and a forming station 3 for forming the packaging as well as a removal and cutting area 4.

A lower web for the lower or tray film is drawn off from a first film roll 5, said lower web being formed in a forming tool 6 under the effect of pressure and heat to form packaging trays or suchlike. In the loading area 7, the packaging trays are filled with the product and subsequently covered with a cover or top film, which is drawn off from a second film roll 8. In forming station 3, the packaging tray and the upper film are joined together and sealed with prior evacuation in a vacuum chamber 9. In the following removal and cutting area 4, the vacuumed packages are trimmed as required by the desired amount at the edges and removed. The loading area is disposed between tool lifters 10. Each tool lifter 10 comprises a tool lifting arrangement with in each case two short-stroke cylinders 11 and tool lifting cylinders 19, a lower tool part 12 which is guided between guide rods 14 and which also carries vacuum chamber 9. The arrangement also includes an upper tool part 12 disposed fixedly and above vacuum chamber 9.

Short-stroke cylinders 11 are coupled with a cylinder shaft 15. Cylinder shaft 15 is provided with a locking cam 16, which has an elliptical cross-section in the direction of motion. In the axial direction of cylinder shaft 15, lower tool part 12 has an identically shaped, but larger opening 17. If, after the lifting of lower tool part 12 into a clamping position of lower tool part 12′ by means of short-stroke cylinders 11, cylinder shaft 15 is rotated through 90°, locking cam 15 cannot pass through opening 16 and blocks the raised lower tool part in the raised position. Short-stroke cylinders 11 are actuated for a high final contact pressure.

The films are fed continuously from film rolls 5, 8 and the individual work cycles of loading the product, forming the lower film, applying the cover film, evacuating/sealing and the product removal take place simultaneously or in a synchronised manner. The movement takes place continuously with short holding phases for the contact pressure of the tools, evacuation and sealing of the packaging.

The mode of functioning of tool lifter 10 is:

In a first step, lower tool part 12 with a carriage and vacuum chamber 9 is traversed upwards into a clamping position 12′ by means of tool lifting cylinder 19 (main lift), wherein locking cam 16 of cylinder shaft 15 passes through opening 17 in lower tool part 12.

Cylinder shaft 15 is then rotated by means of tool closing cylinder 18 through approx. 90° and locking cam 16 thus locks lower tool part 12 in this position (initiation of tool closure), wherein the rotation for the most part takes place without contact with lower tool part 12. Locking cam 16 presses against lower tool part 12 only after the rotation and supports the latter.

Short-stroke cylinders 11 are then acted upon, so that the complete high contact pressure is produced against upper tool part 13.

After evacuation of vacuum chamber 9 and production of the evacuated packaging, tool closing cylinders 18 are deactivated, locking cam 16 is again rotated through approx. 90°, so that it can pass through opening 17 when carriage/lower tool part 12 is lowered.

Exclusively linear movements are performed without forces being applied to bearings as a result of the contact pressure and lubrication-free bearings are possible. Incorrect settings are avoided by largely identical profiles.

List of Reference Numbers

1 vacuum packaging machine

2 working plane

3 forming station

4 removal and cutting area

5 film roll

6 forming tool

7 loading area

8 film roll

9 vacuum chamber

10 tool lifter

11 short-stroke cylinder

12 lower tool part

12′ clamping position of lower tool part

13 upper tool part

14 guided rods

15 cylinder shaft 16 locking cam

17 opening

18 tool closing cylinder

19 tool lifting cylinder 

1. A vacuum packaging machine for producing an evacuated packaging of a product, which is disposed between an upper film and a lower film, wherein the vacuum packaging machine comprises at least one tool lifter (10) with tools, comprising an upper tool part (13) and a lower tool part (12) and a lifting system, which enables a first and a second lifting or closing movement, characterised in that at least one tool lifting cylinder (19) for a vertical lift of the lower tool part (12) as well as a cylinder shaft (15), which is passed through the lower tool part (12) and on which a locking cam (16) is located, is provided, wherein the cylinder shaft (15) is passed through an opening (17) of the lower tool part (12), the cross-section of said opening corresponding to that of the locking cam (16).
 2. The vacuum packaging machine according to claim 1, characterised in that two tool lifters (10) are provided, between which a loading area, or a working plane (2), is disposed.
 3. The vacuum packaging machine according to claim 1 or 2, characterised in that at least one short-stroke cylinder (11) is also provided per tool lifter (10).
 4. The vacuum packaging machine according at least one of claims 1 to 3, characterised in that tool closing cylinders (18) are provided for locking or unlocking the locking cam (16).
 5. A device for performing a tool lift, in particular on a packaging or deep-drawing machine, comprising at least one tool lifter (10) with tools, an upper tool part (13) and a lower tool part (12) as well as a lifting system, which enables a first and a second lifting or closing movement, characterised in that at least one tool lifting cylinder (19) for a vertical lift of the lower tool part (12) and a cylinder shaft (15), on which a locking cam (16) is located, is provided, wherein the cylinder shaft (15) is passed through an opening (17) of the lower tool part (12), the cross-section of said opening corresponding to that of the locking cam (16).
 6. A method for producing an evacuated packaging of a product, wherein the product is disposed between an upper film and a lower film, wherein a first and a second lifting or closing movement of the tool takes place for the forming and sealing of the packaging, in such a way that the first movement is a main movement, which is performed by means of a lifting arrangement, and the second movement is used for the closing/contact pressure of the tool, characterised in that, in a first step, the lower tool part (12) is traversed upwards into a clamping position (12′) by means of tool lifting cylinder (19) and a locking cam (16) of a cylinder shaft (15) is then rotated through approx. 90° by means of tool closing cylinders (18) beneath an opening (17) in the lower tool part (12) and the lower tool part (12) is thus locked in this position and, in a further step, short-stroke cylinders (11) are acted upon in such a way that a complete high contact pressure against the upper tool part (13) is achieved.
 7. The method according to claim 6, characterised in that the locking cam (16) can pass through an opening (17) in the lower tool part (12).
 8. The method according to claim 6 or 7, characterised in that the locking cam (16) can rotate into a locking and passage position.
 9. The method according to at least one of claims 6 to 8, characterised in that, in order to release the tool, the locking cam (16) is again rotated through approx. 90° after release of the contact pressure and can thus pass downwards through the opening (17). 